GM Service Manual Online
For 1990-2009 cars only

Step

Action

Yes

No

Schematic Reference: Automatic Level Control Schematics

1

Did you review the automatic level control suspension system operation and perform the necessary inspections?

Go to Step 2

Go to Symptoms - Automatic Level Control

2

Verify that the automatic level control system does not vent in order to lower the vehicle.

Does the automatic level control system operate normally?

Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems

Go to Step 3

3

  1. Turn ON the ignition, with the engine OFF.
  2. Disconnect the automatic level control height sensor.
  3. Connect a 3 amp fused jumper wire between the automatic level control exhaust solenoid control circuit of the automatic level control height sensor and a good ground.

Does the vehicle lower?

Go to Step 4

Go to Step 8

4

Test the ignition 1 circuit of the automatic level control height sensor for voltage. Refer to Circuit Testing in Wiring Systems.

Is battery voltage present?

Go to Step 5

Go to Step 13

5

Test the automatic level control inflator timer relay circuit of the automatic level control height sensor for voltage. Refer to Circuit Testing in Wiring Systems.

Is battery voltage present?

Go to Step 6

Go to Step 14

6

Test the ground circuit of the automatic level control height sensor for an open circuit and high resistance. Refer to Circuit Testing , Testing for Continuity and Testing for Electrical Intermittents in Wiring Systems.

Did you find the condition?

Go to Step 18

Go to Step 7

7

Replace the automatic level control height sensor. Refer to Automatic Level Control Sensor and Bracket Replacement .

Is the replacement complete?

Go to Step 20

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8

Test the battery voltage circuit of the automatic level control air compressor for voltage. Refer to Circuit Testing in Wiring Systems.

Is battery voltage present?

Go to Step 10

Go to Step 9

9

Repair the open in the battery positive voltage circuit. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

Go to Step 20

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10

Connect a 3 amp fused jumper wire (backprobe) between the automatic level control exhaust solenoid control circuit of the automatic level control air compressor to a good ground .

Does the vehicle lower?

Go to Step 11

Go to Step 12

11

Repair the open in the automatic level control exhaust solenoid control circuit. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

Go to Step 20

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12

Replace the air compressor head. Refer to Automatic Level Control Air Compressor Head Replacement .

Did you complete the replacement?

Go to Step 20

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13

Repair the open in the ignition 1 circuit. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

Go to Step 20

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14

Test the battery positive circuit of the ALC timer relay for voltage.

Is battery voltage present?

Go to Step 16

Go to Step 15

15

Repair the open in the battery positive circuit. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

Go to Step 20

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16

Test the automatic level control inflation timer relay circuit of the automatic level control timer relay for voltage.

Is battery voltage present?

Go to Step 17

Go to Step 19

17

Repair the open in the automatic level control inflation timer relay circuit of the automatic level control timer relay. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

Go to Step 20

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18

Repair the open in the ground circuit. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

Go to Step 20

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19

Replace the automatic level control timer relay. Refer to Automatic Level Control Relay Replacement .

Did you complete the replacement?

Go to Step 20

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20

Operate the system in order to verify the repair.

Did you correct the condition?

System OK

Go to Step 3